Permanent magnet



Cal

.Patented Oct. 19, 1937 UNITED STATES PATENT OFFICE No Drawing.Application October 17, 1935, Se-

rial No. 45,431. In Great Britain May 1, 1934 4 Claims.

This invention relates to magnets and has reference to magnets made fromferrous-nickelaluminium alloys. Y

Steel alloys for permanent magnets containing large percentage ofnickel, and lesser percentages of aluminium, together with certain otherelements are already known, and it is the object of the presentinvention to provide magnets made from an alloy of this general type buthaving a certain specific constitution which, after sub- Jection to aspecial heat treatment hereinafter set out, exhibit enhanced magneticproperties.

' The present invention consists in its broadest aspect of a permanentmagnet composed of from 30% to 35% nickel, from to aluminium, from 0.4%to 4% titanium and the rest iron having a carbon content oi not over0.15%. the' composition being heat treated to render it permanentlymagnetizable by heating to a temperature between 1100 to 1300 C. andquenching in oil, and then heating to between 650 and 800 C. and coolingin air or air blast.

The preferred alloy for use in the manufacture of magnets contains, inaddition to iron, about 32% nickel, 12% aluminium and 2% titanium.Carbon is bound to be present but it is desirable to keep it as low aspossible and preferably the carbon content should not exceed 0.1%. Ithas been found, however, that a carbon content of 0.15% is permissible.

By heat treatment this alloy is made to exhibit desirable magneticproperties. The preferred heat treatment consists in heating to 1280 C.and

' quenching in oil and reheating to 750 C. and

cooling in air blast. After such a treatment the properties of a sampleof the steel having the preferred constitution were found to be:-

Remanence (Bi-em) gausses 5,000 Maximum product (BHmax) of B and H-1,000,000 Coercive force (He) gausses 500 The heat treatment of thealloy to render it permanently magnetimble is approximately the samewith all alloys within the scope of the invention. 10

What I claim and desire to secure by Letters Patent is:-

1. A permanent magnet of steel alloy consisting of 30 to 35% nickel, 10to 15% aluminum, substantially .4 to 4% titanium and the rest iron, 15heat-treated by first being raised to a temperature of between 1100 C.and 1300 C. and quenched in oil followed by heating to substantially 675C. to 775 C. and cooled in air, said magnet having a BHmax of 1,000,000or over and a coercive force of 500 or over.

2. A permanent magnet of steel alloy consisting of substantially 32%nickel, 12% aluminum,

.4 to 2.0% titanium and the rest iron of not over 0.15% carbon,heat-treated by first being raised to a temperature of between 1100 C.and 1300 C. and quenched in oil followed by heating to substantially 675C. to 775 C. and cooled in air, said magnet having a BHmax of 1,000,000or over and a coercive force of 500 or over.

3. A permanent magnet of claim 2 inwhich the titanium content is about.4%.

4. A permanent magnet of claim 2 in which the temperature of the firstheat treatment is about 1280 C. and the temperature of the second heattreatment is about 750 C.

' ALFRED CYRIL CATHERALL.

